Sodic Water Irrigation Research Articles

Can Plant Nutrient Dynamics and Indian Mustard Yield Be Influenced by Addition of Organic Amendments Under Saline Sodic Soils?

ABSTRACT Arid and semi-arid regions are having huge potential for agricultural production but also have limitations of salinity and alkalinity. By mediating rhizospheric environment with the application of organic and inorganic nutrient sources, Indian mustard yield could be enhanced in these areas. For this, a field experiment was conducted to study the effect of organic (FarmYard Manure and vermicompost) and inorganic (urea) amendments with irrigation water of different sodium absorption ratios (SAR; 6, 10, 20 and 30). The experiment was laid out in a split-plot design (SPD) with 24 treatment combinations keeping different SAR in main plots and organic and inorganic nitrogen sources in sub plots. Experiment results revealed that increasing SAR levels reduced the availability of major plant nutrients, i.e. nitrogen, phosphorus and potassium. The soil organic carbon mineralization rate and Indian mustard seed yield were also deceased with increasing levels of SAR. Application of nitrogen through farm yard manure (FYM) and vermicompost decreased the electrical conductivity (EC), pH, and enhanced the cation exchange capacity (CEC) of soil solution. Application of 50% recommended dose of nitrogen (RDN) through urea and 75% through vermicompost produced maximum seed and stover yield of Indian mustard. Thus, supply of recommended dose of nitrogen as inorganic (50%) and organic (75%) sources improved the soil health and Indian mustard yield of arid lands with sodic irrigation water. The use of organic sources in place of sole application of N fertilizer may be a potential management option in sodic groundwater irrigated areas for enhancing mustard crop yield.

Effects of Sodic Water Irrigation and Neutralizing Amendments on Physiological, Biochemical, and Nutritional Quality Traits of Fodder Sorghum

This study was conducted at two farmers’ fields to assess the production potential and quality of summer fodder sorghum intervened between the rice-wheat cropping sequences (RWCS) on high residual alkalinity, i.e., residual sodium carbonate (RSC) water irrigation-induced sodic soil. The treatments were comprised of two field sites having different residual alkalinity [RSC ~5 me L−1 (RSC-1) and ~7 me L−1 (RSC-2) water irrigation in main plots, four neutralization strategies, i.e., control/unamended condition (N0), gypsum @ 7.5 t ha−1 (N1), pressmud @ 10 t ha−1 (N2) and gypsum @ 3.75 t ha−1 + pressmud @ 5 t ha−1 (N3) in sub plots and two varietal sequences of RWCS, i.e., salt tolerant varieties (CSR 30 basmati fb KRL 210) and traditionally grown varieties (PB 1121 fb HD 2967) of rice and wheat as sub–sub plots. Sorghum cv. Sugargraze (Advanta Company) was grown after the harvesting of wheat and cut for green fodder before transplanting rice during both years. Sorghum physiological and biochemical traits [relative water content (RWC), total chlorophyll content, photosynthetic rate (Pn), stomatal conductance (gS), transpiration rate (E), chlorophyll fluorescence (Fv/Fm), photon quantum yield [Y (II)] and K/Na ratio]; fodder quality traits [Crude protein (CP), and ether extract (EE)] and productivity [green fodder yield (GFY), dry matter yield, CP yield, EE yield and ash yield) and profitability (gross returns, net returns, benefit–cost ratio) significantly decreased with the increase in irrigation water RSC from 5 to 7 me L−1. Proline, total soluble sugar (TSS), total soluble protein (TSP), dry matter (DM), ash, neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL), neutral detergent insoluble CP (NDICP) and acid detergent insoluble CP (ADICP) decreased with increasing RSC of irrigation water. Sodicity neutralization considerably improved sorghum physiological adaptation mechanisms, fodder quality, productivity and profitability. The introduction of summer fodder sorghum between RWCS resulted in additional net returns (NR) (INR 13.64 to 20.79 × 103 ha−1). Our results indicate that pressmud proved a feasible alternative to replace and/or reduce the quantity of gypsum required for neutralization of RSC water irrigation. Growing summer fodder sorghum between RWCS along with neutralization of RSC water irrigation can increase the availability of quality green fodder during lean period and also increase the profitability of the rice-wheat cropping system in high residual alkalinity water irrigation conditions.

Soil fertility, microbial dynamics and mustard yield potential mediated by addition of organic amendments under sodic irrigation water

ABSTRACT Use of saline-sodic irrigation water degrades soil health and reduced mustard yield, particularly in India’s low-rainfall regions. This research was conducted to assess the effect of sodic water and nitrogen sources on soil organic carbon (SOC), microbial biomass, soil enzymatic activities, and interaction effects on mustard seed yield. The experiment was laid out in split-plot design comprising four levels of sodium adsorption ratio (SAR) of water (6, 10, 20, and 30) and six nitrogen sources [(control, 125% recommended dose of nitrogen (RDN) through urea, 75% RDN+50% RDN through farm yard manure (FYM), 75% RDN through urea+50% RDN through vermicompost (VC), 50% RDN through urea+75% RDN through FYM, 50% RDN through urea+75% RDN through VC]. The use of high SAR irrigation water caused a significant reduction in soil fertility and microbial parameters. The combined use of chemical fertilizers, FYM, and vermicompost significantly increased microbial activities (64.9% SMB-C), SOC (23.5%), soil enzyme activity (dehydrogenase and alkaline phosphates), and mustard seed yield (49%). The use of 50% RDN via urea+75% RDN via VC was suggested as a better technology for minimizing the adverse effect of high SAR water on crop yield.

Effect of Zn and Fe Enriched FYM on Yield, Nutrient Content and Uptake by Cowpea Irrigated with Sodic Water

A pot experiment was conducted during kharif 2018-19 at S.K.N. College of Agriculture, Jobner (Rajasthan) to study the “Effect of Zn and Fe enriched Farmyard manure on nutrient availability and yield of cowpea [Vigna ungiculata (L.)wilczek] under sodic water irrigation” to evaluate the effect of different sodic water and sources of Zn and Fe on yield, nutrient concentration and uptake by cowpea on loamy sand soil. The experiment comprising of 15 treatment combinations replicated three times, was laid out randomized block design with three levels of sodic water (2, 4 and 6 mmol L-1 ) and five levels of sources of Zn and Fe (0, ZnSO4.7H2O, FeSO4.7H2O, Zn enriched FYM, Fe enriched FYM) as variables. The total and number of nodules per plant, nodule index, pods per plant and seeds per pod were counted at stage and harvesting respectively. Results revealed that under 6 mmol L-1 Residual sodium carbonate of irrigation water, the seed and straw yield of, nutrient concentration and uptake viz., P, K, Zn and Fe in seed and straw decreased significantly with all levels of sodic water and maximum reduction was recorded with the application of 6 mmol L-1 of sodic water, while N in seed and straw, protein content in seed increased significantly. The application of Zn enriched FYM increased seed and straw yield , nutrient concentration and uptake viz., N, P, K, Zn and Fe in seed and straw, protein content in seed.

Effect of saline and sodic irrigation water on soil properties after harvest of Bajra crop

A pot experiment was conducted during summer-2020 at Net House, Department of Agricultural Chemistry and Soil Science Junagadh Agricultural University, Junagadh to assess four levels for each of salinity (2, 4, 6 and 8 dS m-1) and sodicity (5.0, 10.0, 15.0 and 20.0 SAR) of irrigation water on bajra by adopting factorial CRD with three replications. The results indicated that application of different levels of saline and sodic irrigation water produced significant effect on soil properties after harvest of bajra crop. The highest organic carbon and available macronutrients (N, P2O5 and K2O kg ha-1) of soil were observed with with EC 2 dS m-1 and SAR 5.0 and the lowest with EC 8 dS m-1 and SAR 20.0 of irrigation water. The water soluble and exchangeable Ca, Mg and Na were found maximum with EC-8 dS m-1, whereas water soluble and exchangeable K found maximum with EC-2 dS m-1 and soil properties like EC2.5, ECe, CEC found maximum with EC-8 dS m-1 whereas pH2.5, pHs and ESP found maximum with EC-2 dS m-1 level of saline irrigation water. The water soluble and exchangeable Na was found maximum with SAR- 20.0, whereas water soluble and exchangeable Ca, Mg and K were found maximum with SAR- 5.0. The soil properties like EC2.5, ECe, pH2.5, pHs and ESP of the soil was found minimum with SAR-5.0 and found maximum with SAR- 20.0, but CEC was found maximum with SAR- 5.0 level of sodic irrigation water. The effect of saline and sodic irrigation water was found significant on available N and water-soluble cations Ca++, Mg++, Na+, K+, exchangeable cations Ca++, Mg++, Na+, CEC, ESP, EC2.5 and ECe of soil after harvest of Bajra.

Influence of saline and sodic irrigation water on Bajra- II : Effect on concentration and uptake of nutrient

A pot experiment was conducted at Net House, Department of Agricultural Chemistry and Soil Science Junagadh Agricultural University, Junagadh to assess the different levels of saline and sodic irrigation water on content and uptake of nutrient by bajra during the summer-2020. The treatment consist of four levels for each of salinity (2, 4, 6 and 8 dS m-1) and sodicity (5.0, 10.0, 15.0 and 20.0 SAR) of irrigation water on Bajra by adopting factorial CRD with three replications. The results indicated that application of different levels of saline and sodic irrigation water produced significant effect on concentration and uptake of N, P and K by grain and fodder of bajra crop.The highest N, P and K content (1.11%, 0.31% and 0.60 %) and uptake (225.5, 62.6 and 121.2 mg pot-1) by grain and content (0.88 %, 0.21% and 0.33%) and uptake (976.0, 225.8 and 362.5 mg pot-1) by fodder were observed with EC 2 dS m-1 level of salinity of irrigation water and the lowest content and uptake by grain were observed with EC 8 dS m-1 level of salinity of irrigation water, respectively. While the highest N, P and K content (1.15%, 0.30% and 0.59%) and uptake (256.9, 67.5 and 131.4 mg pot-1) by grain and content (0.98%, 0.19% and 0.34%) and uptake (1072.7, 210.6, 370.2 mg pot-1) by fodder were observed with SAR-5.0level of sodicity of irrigation water and the lowest content and uptake by grain were observed with SAR-20.0level of sodicityof irrigation water. The interaction effect between salinity and sodicity levels of irrigation water on uptake of N by grain and fodder where found significantly the highest with C1× S1(EC-2.0 dSm-1 ×SAR-5.0) level of salinity and sodicity of irrigation water.

Influence of saline and sodic irrigation water on Bajra- I : Effect on yield and yield attributes

A pot experiment was conducted at Net House,Department of Agricultural Chemistry and Soil Science,Junagadh Agricultural University, Junagadh to assess four levels each of salinity (2, 4, 6 and 8 dS m-1) and sodicity (5.0, 10.0, 15.0 and 20.0 SAR) of irrigation water on Bajra by adopting factorial CRD with three replications.The results indicated that application of different levels of saline and sodic irrigation water produced significant effect on growth, yield attributes, yield and quality of bajra crop. The maximum plant height, number of effective and total tillersper plant, germination percentage, earhead girth, grain, fodder and biological yield and harvest index were observed with EC 2 dS m-1 and SAR 5.0 and the lowest with EC8 dS m-1and SAR 20.0 of irrigation water. The quality parameters like seed index and protein content were found maximum with saline irrigation water level of EC 2 dS m-1 and SAR 5.0 and the lowest with EC 8 dS m-1 and SAR 20.0 of irrigation water. The interaction effect between salinity and sodicity levels of irrigation water onfodder yield, harvest index were found significantly the highest with C1× S1(EC-2.0 dSm-1×SAR-5.0) and plant height were found significantly the highest with C2× S1(EC-4.0 dSm-1× SAR-5.0) at 60, 90 DAS and at harvest.

Hysteresis in soil hydraulic conductivity as driven by salinity and sodicity – a modeling framework

Abstract. Declining soil-saturated hydraulic conductivity (Ks) as a result of saline and sodic irrigation water is a major cause of soil degradation. While it is understood that the mechanisms that lead to degradation can cause irreversible changes in Ks, existing models do not account for hysteresis between the degradation and rehabilitation processes. We develop the first model for the effect of saline and sodic water on Ks that explicitly includes hysteresis. As such, the idea that a soil's history of degradation and rehabilitation determines its future Ks lies at the center of this model. By means of a “weight” function, the model accounts for soil-specific differences, such as clay content. The weight function also determines the form of the hysteresis curves, which are not restricted to a single shape, as in some existing models for irreversible soil processes. The concept of the weight function is used to develop a reversibility index, which allows for the quantitative comparison of different soils and their susceptibility to irreversible degradation. We discuss the experimental setup required to find a soil's weight function and show how the weight function determines the degree to which Ks is reversible for a given soil. We demonstrate the feasibility of this procedure by presenting experimental results showcasing the presence of hysteresis in soil Ks and using these results to calculate a weight function. Past experiments and models on the decline of Ks due to salinity and sodicity focus on degradation alone, ignoring any characterization of the degree to which declines in Ks are reversible. Our model and experimental results emphasize the need to measure “reversal curves”, which are obtained from rehabilitation measurements following mild declines in Ks. The developed model has the potential to significantly improve our ability to assess the risk of soil degradation by allowing for the consideration of how the accumulation of small degradation events can cause significant land degradation.

Zinc fractions and Barley productivity under zinc fertilization and sodic irrigation water management

An experiment was conducted to know the effect of different residual sodium carbonate (RSC) water, farmyard manure (FYM) and different levels of zinc fertilization on different zinc fractions of soil, yield attributes and yield of barley in loamy sand soil under semi-arid climatic conditions. The three levels of RSC of irrigation water (2.5, 5 and 10 mmol/ L), two levels of FYM (control and 15 t/ha) and four levels of zinc (control, 15, 30 and 45 kg ZnSO4/ha) were evaluated on barley production in split plots design. Results indicated that application of high RSC irrigation water (10 mmol/ L) significantly reduced the different fractions of soil Zn (except Occ-Zn), plant height, total and effective tillers, test weight and yield of barley during both the years, while 5 mmol/L of RSC irrigation level found at par with 2.5 mmol/L. Application of FYM significantly increased the different Zn fractions in soil (except Occluded- Zn) as well as yield attributes, grain and straw yield of barley. The increasing level of zinc application significantly increased the different fractions of soil Zn (except Occ-Zn), available soil Zn, yield attributes and yield of barley. It was observed that the grain yield of barley positive and significantly correlated with different fractions of Zn, viz. DTPA-Zn (r=0.888), Ads-Zn (r=0.525), Occ-Zn (r = 0.670), OC-Zn (r = 0.948) and Res-Zn (r = 0.923). The optimum dose of zinc for barley computed as 37.6 kg / ha ZnSO4 with corresponding optimum yield of 4365 kg/ha.

Soil properties as influenced by use of water having variable salinity and sodicity

A pot experiment was conducted during summer season of 2018 at Net House, Department of Agricultural Chemistry and Soil Science, College of Agriculture, Junagadh Agricultural University, Junagadh to study the influence of different levels of saline and sodic irrigation water on soil properties. The treatment consists of four levels each of salinity (2, 4, 6 and 8 dS m-1) and sodicity (5.0, 10.0, 15.0 and 20.0 SAR) of irrigation water by adopting factorial CRD with three replications. The available macronutrients (N, P2O5 and K2O) and organic carbon of soil after harvest of the crop were found maximum with EC-2 dS m-1 and SAR-5.0 level of irrigation water. The water soluble and exchangeable Ca, Mg and Na and soil properties like EC2.5, ECe, pH2.5, pHs, CEC and ESP was found maximum with EC-8 dS m-1 while water soluble and exchangeable K was found maximum with EC-2 dS m-1. The water soluble and exchangeable Na was found maximum with SAR-20.0, whereas water soluble and exchangeable Ca, Mg and K were found minimum with SAR- 20.0. The soil properties like ECe, pH2.5, pHs and ESP of the soil was found maximum with SAR- 20.0, but CEC was found maximum with SAR-5.0. The combined effect of saline and sodic irrigation water was found significant on available N and water soluble cations Ca++, Mg++, Na+, K+, exchangeable Na+, ESP, ECe and pH2.5 of soil after harvest of groundnut.

Influence of water having variable salinity and sodicity on groundnut-II : Effect on nutrient content and uptake

A pot experiment was conducted at Net House, Department of Agricultural Chemistry and Soil Science, College of Agriculture, Junagadh Agricultural University, Junagadh to assess the different levels of saline and sodic irrigation water on content and uptake of nutrient by groundnut during the Summer-2018. The treatment consists of four levels each of salinity (2, 4, 6 and 8 dS m-1) and sodicity (5.0, 10.0, 15.0 and 20.0 SAR) of irrigation water by adopting factorial CRD with three replications. The results indicated that application of different levels of saline and sodic irrigation water produced significant effect on content and uptake of N, P and K by kernel and haulm of groundnut. The highest N, P and K content (3.76 %, 0.34 % and 0.67 %) and uptake (163.6, 13.34 and 25.14 mg pot-1) by kernel and content (1.08 %, 0.15 % and 0.40 %) and uptake (177.8, 25.01 and 66.5 mg pot-1) by haulm, respectively were observed with EC-2 dS m-1 level of salinity of irrigation water, but the lowest content and uptake by kernel were observed with EC-6 dS m-1 and by haulm at EC-8 dS m-1 levels of salinity of irrigation water. There was no any pod formation were observed with EC-8 dS m-1, hence, content and uptake of nutrients by kernel considered zero. While the highest N, P and K content (2.85 %, 0.22 % and 0.42 %) and uptake (109, 5.93 and 11.45 mg pot-1) by kernel and content (1.01 %, 0.13 % and 0.37 %) and uptake (135.5, 17.80 and 48.6 mg pot-1) by haulm, respectively were observed with SAR- 5.0 level of sodicity of irrigation water. The interaction effect between salinity and sodicity levels of irrigation water on concentration and uptake of N by kernel and haulm were found significantly the highest with C1×S1 (EC- 2.0 dS m-1 × SAR- 5.0) level of salinity and sodicity of irrigation water.

Influence of water having variable salinity and sodicity on groundnut- I : Effect on growth, yield attributes, yield and quality

A pot experiment was conducted at Net House, Department of Agricultural Chemistry and Soil Science, Junagadh Agricultural University, Junagadh to assess four levels each of salinity (2, 4, 6 and 8 dS m-1) and sodicity (5.0, 10.0, 15.0 and 20.0 SAR) of irrigation water on groundnut by adopting factorial CRD with three replications. The results indicated that application of different levels of saline and sodic irrigation water produced significant effect on growth, yield attributes, yield and quality of groundnut crop. The maximum plant height, number of mature and immature pods plant-1, weight of mature and immature pods plant-1, days to 50 % flowering, pod and haulm yield and harvest index were observed with EC 2 dS m-1 and SAR 5.0 and the lowest with EC 8 dS m-1 and SAR 20.0 of irrigation water. The quality parameters like seed index and protein content were found maximum with the saline irrigation water level of EC-2 dS m-1 and SAR-5.0, but there was no any pod formation recorded with EC-8 dS m-1. The interaction effect between salinity and sodicity levels of irrigation water on pod (8.10 g pot-1), kernel (5.36 g pot-1) and biological (26.61 g pot-1) yield were found significantly the highest with C1×S1 (EC- 2.0 dS m-1×SAR- 5.0) while no any pod formation were observed with C4×S1, C4×S2, C4×S3 and C4×S4 level of irrigation water.

Soil Degradation Risks Assessed by the SOTE Model for Salinity and Sodicity

AbstractSoil salinity and sodicity are serious environmental hazards, with the potential to limit agricultural production and cause destructive soil degradation. These concerns are especially high in dry areas, which often rely on saline and sodic irrigation water to support agriculture. To assess long‐term soil degradation risk, we introduce the Salt of the Earth (SOTE) model, which describes the dynamics of soil water content, salinity, and sodicity, as driven by irrigation and rainfall. The SOTE model incorporates how changes in salinity and sodicity affect saturated soil hydraulic conductivity, Ks, on a soil‐specific basis. The model was successfully validated against results from a multiyear lysimeter experiment involving different irrigation water qualities and precipitation. We evaluated the impact of shorter rainy seasons on the dynamics of soil degradation in a Mediterranean climate. Critical degradation risk, indicated by reductions in Ks greater than 20%, increased from 0% to 3% when the rainy season was shortened from 130 to 80 days. Alarmingly, when irreversible degradation is allowed for, overall risk increases to 68%. Assessing the effect of irrigation water on different soils textures, we found that while greater clay fractions are usually more susceptible to dispersion, accurate risk assessment hinges on soil water dynamics. SOTE is amenable to large‐ensemble simulations of stochastic climatic conditions, for which trends in the statistics of salinization and soil degradation can be identified. As such, SOTE can be a useful land management tool, allowing planners to understand the risk of long‐term soil degradation given irrigation practices, soil qualities, and climate conditions.

Available nutrients and labile carbon fractions in soil irrigated with sodic water

An ongoing long-term field experiment established in the year 1994 at Vegetable Science Research Farm, CCS HAU, Hisar, India under different vegetable cropping systems was selected to study the effects of sodic water irrigation, gypsum and farmyard manure on labile soil organic carbon fractions and available nutrients in soil. The present study was conducted after 20 years of experimentation during 2014-2015. The field was irrigated with high RSC (11.5 me/l) sodic water having three treatment levels each of gypsum, viz G0 control, G1=50 % neutralization of RSC, G2=100% neutralization of RSC, as well as FYM (F0 = control, F1= 10 tons/ha, F2 =20 tons/ha) in a sandy loam Typic Ustochrept. Results showed that the pH of soil was very high under F0G0, and it decreased with the use of FYM and gypsum as amendments, however a reverse trend was observed in electrical conductivity. There was an increase in different carbon fractions and available nutrients when FYM was applied over no FYM application. Application of gypsum increased microbial biomass carbon, light fraction carbon and available nutrients (N, P, S) content in the soil but dissolved organic carbon and available K content was found decreased. It can be concluded that application of FYM @20 t/ha along with gypsum @100% neutralization of RSC of irrigation water should be applied for maintaining soil quality and productivity.

Effect of fym and gypsum on distribution of micronutrient in soil under sodic water irrigation: A long-term study

Micronutrient deficiency is major constraints in crop production as well as crop quality. Deficiency of micronutrients in soil leads to lower micronutrient content and thereby causing health problem in animals and human being. Long-term field experiment under different vegetable cropping system was established in 1994 at the vegetable science research farm, CCS HAU, Hisar, India to study the effects of sodic water irrigation, gypsum and FYM on soil available micronutrients and soil properties. The field was irrigated with high RSC (11.5 me L−1) sodic water having three levels of gypsum (G0 = control, G1 = 50% neutralization of RSC), G2 = 100% neutralization of RSC, as well as FYM (F0 = control, F1 = 10 t ha−1, F2 = 20 t ha−1) in 2014–15 on a sandy loam Typic Ustochrept having 19.6% clay and 9.3 cmol(p+)kg−1 soil CEC in 0–30 cm layer. Electrical conductivity, available micronutrients (Mn, Cu, Fe and Zn) increased with increase in levels of FYM 0 to 20 t ha−1 and gypsum from 0 to 100% neutralization of RSC, respectively. The pH of soil was very high under F0G0 and decreased with the use of FYM and gypsum as amendments. These results indicate that the combined use of FYM and gypsum improved soil health and maintained the sustainability of the different vegetable cropping system.

Reclaimation of Sodic Bore Well Water for Irrigation through Gypsum Treatment at Anbil Dharmalingam Agricultural College and Research Institute, Trichirapalli District, Tamil Nadu

It is necessary to ascertain the quality of irrigation water at Anbil Dharmalingam Agricultural College and Research Institute farm in order to monitor the possible effects of the sodic irrigation water on the soil. Irrigation with sodic water enhances soil sodicity built up in soils of experimental farm which leads to adverse effects on soil physical, chemical and biological properties, not fitted for farming. In areas where ground water is sodic and where good quality surface water supplies are either inadequate or not available at all and the farmers are left with no option but to use sodic ground water for irrigation purposes, which pose grave risks for soil health and environment. The quality of sodic water can be improved by treating with gypsum. Due to gypsum dissolution calcium and sulphate ions come in soluble form in irrigation water. Research conducted at Anbil Dharmalingam Agricultural College and Research Institute Trichy for reclamation of sodic bore well water revealed that the sodic bore water samples collected from bore well 1 (AMP shed) having initial Residual Sodium Carbonate (RSC) of 8.0 meq /lit and bore well 6 (Boys hostel) having initial RSC of 6.2 meq /lit indicated the decrease in RSC upto - 0.6 meq / l and 1.2 meq / l respectively due to gypsum treatment with 0.1 per cent (12.50 tons/ha) and 0.35 per cent ( 43.75 tons /ha ) at the retention time of 1 hour to irrigate 1 ha paddy field throughout crop establishment stage. It was concluded that for lowest retention time higher doses of gypsum was required for sodic water reclamation. As we increased the retention time, the required gypsum quantity was also minimized as observed for bore well 1 (AMP shed 8 meq/l)) sodic water samples with gypsum dose of 0.15 per cent (18.75 tons /ha) with the retention time of 4 hours. These findings were very much helpful for the farmers of Manikandam block, Tiruchirappallii district having secondary sodicity built up in soils due to sodic water irrigation during summer.

Effects of sodic water irrigation on growth, physiological relations and ion uptake in two Ziziphus rootstocks

We studied the effects of sodic irrigation on growth, physiological parameters and mineral partitioning in Zizyphus rotundifolia (ZR) and Z. spina-christi (ZS) seedlings used as rootstocks for Indian jujube scion cultivars. Plants grown in normal soils were irrigated with fresh (control) and three kinds of sodic waters having residual sodium carbonate (RSC) levels of 3, 6 and 9 meq/l. Both the species displayed appreciable decreases in fresh and dry weights of shoots and roots at RSCiw level of 9 meq/l. Leaf chlorophyll and chlorophyll fluorescence also decreased with increasing sodicity. While leaf proline content remained unchanged up to RSCiw 3 meq/l, plants treated with 9 meq/l sodic water had nearly twofold higher leaf proline than control indicating that it could play a major role in osmotic adjustment in salt stressed plants. Na+ and Cl- contents increased while K+ and Ca2+ declined in different plant parts with increase in RSCiw. Na+: K+ ratio was higher at a given RSCiw in leaves and roots of ZS and in stems and roots of ZR reflecting better Na+ exclusion by ZR. ZR leaves also had less Cl- than ZS at a given RSCiw. Owing to these adaptive traits, both the species could tolerate RSCiw up to 6 meq/l.

Effect of Sodic Irrigation Water on Organic Carbon and Nitrogen Concentrations, Fluxes and Exports from Newly Installed St. Augustine Grass Sod in South-Central Texas

Population growth in towns and cities requires new construction of homes and conversion of native land use to urban and suburban landscapes. Municipal tap water is generally used for irrigating these urban and suburban landscapes and its water quality can differ globally dependent on whether it is sourced from ground or surface waters. We examined runoff dissolved organic carbon (DOC) and organic nitrogen (DON) concentrations, fluxes and exports from newly installed, fertilized and unfertilized St. Augustine (Stenotaphrum secundatum (Walt.) Kuntze ‘Raleigh’) sod irrigated with a sodic municipal tap water during two 5-week establishment periods (August and September). In unfertilized plots, concentrations of DOC in runoff significantly increased from 20.5 to 73.7 mg L-1 and from 29.6 to 113.3 mg L-1 Runoff concentrations of DOC in fertilized plots significantly increased from 27.3 to 72.0 mg L-1 and from 30.0 to 120.3 mg L-1. Concentrations of DON in runoff did not increase in either unfertilized or fertilized plots. Total DOC exports were 2036 ± 803 kg km-2 and 3341 ± 227 kg km-2 and DON exports were 99 ± 43 kg km-2 and 134 ± 15 kg km-2 respectively for the two turfgrass installation dates for the unfertilized plots. Fertilization had no significant effect on DOC and DON exports (p = 0.29 and 0.18). Na+, K+, Mg2+ and Ca2+ were implicated in both DOC and DON fluxes suggesting that as resources for irrigation water for urban landscapes decline and alternative irrigation water supplies such as grey and black water are utilized we would expect, due to their higher Na+ content that DOC and DON fluxes to urban watersheds will increase.

Long-Term Impact of Cyclic Use of Sodic and Canal Waters for Irrigation on Soil Properties and Crop Yields in Cotton–Wheat Rotation in a Semiarid Climate

A 12-year field experiment (1996–2008) was conducted on a sandy loam soil under semiarid climate to study the impact of use of sodic water (SW) and canal water (CW) in various cyclic modes in a cotton–wheat rotation. Treatments included irrigation with CW and SW (residual sodium carbonate 10 meq L−1) and different variants of cyclic modes of CW and SW irrigation. Irrigation with SW caused increase in pH, electrical conductivity (EC), exchangeable sodium percentage (ESP) that resulted in reduced cotton and wheat yields. The mean yield reduction after 6 years was more for seed-cotton (28%) than for wheat (15%); yield reduction in cotton and wheat after 12 years was 35 and 22%, respectively. Cyclic irrigation of CW and SW resulted in lower pH, EC and ESP than under SW irrigation and increased mean yields of both crops. Cyclic treatments starting with CW involving one SW (2CW:SW, CW:SW) or starting with one SW followed by 2CW irrigations (SW:2CW) produced optimum (>90% yields relative to CW) wheat and seed-cotton yields after 6 years. These cyclic modes could sustain optimum crop yields even after 12 years. Reduction in cotton yield after 6 years was more (18%) than in wheat (10%) in cyclic modes starting with SW involving one CW (SW:CW, 2SW:CW). However, extent of reduction in seed-cotton (25%) and wheat yields (17%) after 12 years made these treatments unsustainable on long-term basis. Based on sustainable yield index and buildup of sodicity, 2CW:SW treatment was found to be the most sustainable among various cyclic modes for the cotton–wheat rotation.

Evaluation of the effects of FYM and gypsum on onion (Allium cepa L.) production under sodic water irrigation

A field experiment was conducted at CCS Haryana Agricultural University, Hisar to study the effect of FYM and gypsum on onion (Allium cepa L.) production under sodic water irrigation. Treatments comprised of three levels of farm yard manure (FYM) (F0- no FYM, F1- 10 t/ha and F2- 20 t/ha FYM) and three levels of gypsum (G0- nogypsum, G1- 50% neutralization of RSC and G2- 100% neutralization of RSC) in addition to control (irrigation with sodic water and no FYM and no gypsum F0G0). Results of the study showed that the seedling mortality was maximum (77.50 %) in control (F0G0) treatment, while minimum number of seedlings mortality (18.17 %) was observed in (F2G2) treatment followed by (25.17 %) (F2G1) treatment. There was significant increase in growth and yield of onion with application of FYM and gypsum. Moreover, maximum bulb yield (180.83 q/ha) was recorded in (F2G2) followed by F2G1 (152.22 q/ha) where 100% sodicity of water was neutralized by the application of gypsum and 20 t/ha FYM. Under sodic water conditions, increasing level of gypsum and FYM help in reducing the sodicity of irrigation water and thereby, increasing the yield of onion. The study concluded that in present situation of scarcity of good quality water for agricultural purposes, use of amendments like FYM and gypsum were best alternative for the best possible use of poor quality ground water and simultaneously sustain the yield of vegetable crops like onion which are sensitive to sodic water.